1). Field of the Invention
This invention relates to an electronic assembly having a decoupling capacitor and to a method according to which it is constructed.
2). Discussion of Related Art
Integrated circuits are usually manufactured in and on semiconductor wafers that are subsequently diced or singulated into individual microelectronic dies. Such a microelectronic die is usually mounted to a package substrate for purposes of providing rigidity thereto and through which signals can be provided to and from the integrated circuit. Such a package substrate often has an array of solder ball interconnection members, also referred to as a ball grid array (BGA), on an opposing surface that are placed on electric lands of a motherboard and, by a thermal reflow process, soldered thereto.
Such a motherboard usually includes a carrier substrate with a power plane and a ground plane therein. A power source is connected to the power plane, and the ground plane is connected to ground. The power and ground planes are connected to separate ones of the electric lands. In addition, input and output (IO) signal sources are connected to other ones of the electric lands. Power, ground, and IO signals can thus be provided through the motherboard, the solder ball interconnection members, and the package substrate to and from the integrated circuit in the microelectronic die.
In order to reduce inductive-capacitance delay, it is usually advantageous to include one or more decoupling capacitors having opposing terminals connected to the power and ground planes. An existing technique is to connect a capacitor between two of the solder ball interconnection members before the solder ball interconnection members are located on the electric lands of the motherboard. Such a process is expensive because it requires additional manufacturing steps, including the placement of the capacitor, and controlled heating and cooling of the solder ball interconnection members so that they reflow over capacitor terminals of the capacitor. These steps have to be carried out before the package (i.e., the combination of the package substrate, the microelectronic die, the solder ball interconnection members, and the capacitor) are shipped to an entity that does the final assembly on the motherboard.